Can A Diet Really Protect The Brain?

According to U.S. News’ annual diet ranking, the classic Mediterranean Diet ranks Number 2. And right behind it at Number 3 is the newer MIND diet, developed by a team at Rush University. The acronym stands for "Mediterranean-DASH Intervention for Neurodegenerative Delay," and as the name suggests, is an amalgam of the Mediterranean and DASH diets. (The latter is a blood pressure-reducing diet developed by the NIH.)

The Mediterranean and MIND diets are both celebrated for their brain-healthy effects—they're thought to reduce the brain shrinkage that comes naturally with age, and even to reduce the risk for cognitive decline and Alzheimer’s disease. But how strong is the research there to suggest that a diet could actually protect the brain, and make the difference between brain health and disease? The short answer is that it’s actually fairly strong, but the research is still a work in progress. So the perfect brain diet will likely get tweaked a bit in the coming years, as we learn more about the specific foods that make a difference in brain health.

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The MIND vs. the Mediterranean

The MIND diet is similar to the Mediterranean diet, except it was designed by scientists, and its components based on what studies have shown help and harm the brain over time. It’s comprised of 10 food groups that should be consumed regularly: Leafy greens, other vegetables, nuts, berries, beans, whole grains, fish, poultry, olive oil and wine. And five that we should leave out: Red meat, butter/margarine, cheese, sweets and fried or fast food.

This sounds a lot like the Mediterranean diet, with a few exceptions. It doesn’t suggest you eat multiple servings of fish per week—one serving should do, the authors say, based on research finding that one serving of fish per week is linked to better brain health, but more than one serving, not so much. And the MIND diet doesn’t suggest you eat fruit other than berries (blueberries are particularly encouraged), since here again, research has simply not shown fruit to help protect the brain. Leafy greens are given their own category in the MIND diet, since research has also shown these to be linked to brain and cognitive health over time.

It’s worth pointing out again that the MIND diet is a variant of the Mediterranean diet, which itself is linked to brain health, with a few science-based tweaks. As more research comes in, the diet will likely get some more, but for now, it seems to take into account the research on the foods that do and don’t help the brain over time.

Diets and Brain Volume

The research linking diet to brain health in the form of brain volume is certainly coming in. A small new study in the journal Neurology finds that people who stick more closely to the Mediterranean diet over time have less brain shrinkage as they age. The researchers looked at brain scans from 401 people in their 70s who agreed to do MRI scans the beginning and end of a three-year period. Those who stuck more closely to the diet had significantly less brain shrinkage over those three years, compared to people who didn’t eat it so much. The size of the effect, the authors calculated, is equivalent to about half the effect of the aging process—which is to say it’s a significant amount.

The team didn’t find that meat or fish were linked to the effect (more on this later), but also suggest that it may be all the foods together help the brain. "It's possible that other components of the Mediterranean diet are responsible for this relationship, or that it's due to all of the components in combination," study author Michelle Luciano said in a news release.

Past research has found similar connections. One study a couple of years ago from NYU looked at correlation between diet and cortical volume in healthy participants. They divided the late middle-aged participants into high and low adherence to the Mediterranean diet, and scanned their brains with MRI. Those who stuck to the diet less closely had more thinning of the cortex in several regions, including those known to be affected in Alzheimer’s disease. Again, the brain naturally atrophies a bit with age, but in this study, the healthy participants who ate a Mediterranean diet had less of that shrinkage. And this was independent of other variables, including whether people carried or didn’t carry the gene associated with Alzheimer’s disease.

Diets and Cognitive Decline

Martha Clare Morris, the nutritional epidemiologist at Rush University who developed the MIND diet, has done a lot of work on these questions over the years. Her work has found that both the Mediterranean diet and the DASH diet are associated with a reduced risk of cognitive decline in older adults, hence her development of the MIND diet.

Morris’ research has shown that the MIND diet is linked to significantly slower cognitive decline in older people who observe the diet over the years. In one study, participants were followed for an average of 4.5 years, and up to 10 years. Those who observed the MIND diet more closely had better scores in global cognition, as well as in five sub-domains: episodic memory, working memory, semantic memory, visuospatial ability, and perceptual speed. Even when potentially confounding variables were taken into account, like education or exercise level, the results held strong. “The rate reduction for persons in the highest tertile [i.e., the top third] of diet scores compared with the lowest tertile was the equivalent of being 7.5 years younger,” the authors write.

Previous studies have found the same thing. One study in elderly people living around Athens—presumably a good setting to study a Mediterranean diet—found that the diet was linked to less cognitive decline over time. And a review study in the journal Epidemiology a few years ago found that people who tended to eat a Mediterranean diet had a reduced risk of both cognitive decline and Alzheimer’s disease.

Diets and Alzheimer’s Disease

Studies have also suggested that what we eat can strongly affect the development of Alzheimer’s disease itself. Morris’ work has found that the MIND diet is linked to reduced risk of Alzheimer’s disease. People who stuck most closely to the MIND diet had about a 53% reduction in the risk of being diagnosed with Alzheimer’s disease—but even for people who followed it moderately, their risk was lowered by 35%. The Mediterranean diet was also linked to reduced risk of Alzheimer’s disease, but only if people stuck to it fairly devoutly. But both diets had an effect. “This suggests that the MIND diet is not specific to the underlying pathology of [Alzheimer’s disease] but perhaps better overall functioning and protection of the brain.”

And other research has arrived at similar connections. A meta-analysis a few years ago from the Mayo Clinic looked at people who followed the Mediterranean diet more or less closely. Those in the top third had a 33% reduced risk of having any kind of cognitive decline, including Alzheimer’s disease, compared to those in the lowest third. Healthy people who stuck more closely to the diet also had a 27% reduced risk of developing mild cognitive impairment and a 36% reduced likelihood of Alzheimer’s disease in the future.

What’s Responsible for the Effect?

It’s not totally clear which part of the diet is behind the Mediterranean/MIND diet effect, and different studies have pointed to different components. As mentioned above, fish wasn’t linked to brain volume in the recent study, which is somewhat surprising. Previous studies have linked fish and omega-3 fatty acid consumption to a reduced risk of cognitive decline. Other experts have argued that the omega-3 component may be responsible, since the healthy fats are known to act as antioxidants, to increase brain cells’ membrane permeability, and are linked to reduced formation amyloid-beta. But perhaps one needs more components than just fish for the diet to be effective.

And other studies have pointed to other factors. In the one mentioned earlier on Athens residents, the authors found that vegetables were most strongly linked to the benefit. It may be that antioxidants in vegetables help repair damage to brain cells and therefore slow brain shrinkage and cognitive decline. Other studies have found that vegetables, but not fruit, are linked to slower cognitive decline and reduced risk of dementia itself. Another study, in women only, found that leafy greens and cruciferous vegetables (but again, not fruits) were linked to slower cognitive decline.

The one exception to the fruit finding has been that berries, with all their antioxidants, do appear to be linked to slower rates of cognitive decline. And as mentioned, berries, especially blueberries, are a key component of the MIND diet.

Finally, red wine—which is also a component of both the Mediterranean and MIND diets—has been thought to play a role in cognition, since its antioxidants may help protect the brain. Some studies have suggested that a little red wine is linked to better cognition as people age, and less likelihood that cognitive decline will progress to dementia.

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More work will need to be done here, but it does seem very likely that what we eat can affect brain health, particularly over the long term. As more research rolls in, the optimal brain diet may need to be adjusted, but for now the components that make up the brain-healthiest diets seem pretty well-illustrated. So have some wine and kale, and leave the pastries out.